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177 lines
4.8 KiB
177 lines
4.8 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/compiler.h> |
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#include <linux/context_tracking.h> |
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#include <linux/errno.h> |
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#include <linux/nospec.h> |
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#include <linux/ptrace.h> |
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#include <linux/syscalls.h> |
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#include <asm/daifflags.h> |
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#include <asm/debug-monitors.h> |
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#include <asm/exception.h> |
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#include <asm/fpsimd.h> |
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#include <asm/syscall.h> |
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#include <asm/thread_info.h> |
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#include <asm/unistd.h> |
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long compat_arm_syscall(struct pt_regs *regs, int scno); |
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long sys_ni_syscall(void); |
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static long do_ni_syscall(struct pt_regs *regs, int scno) |
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{ |
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#ifdef CONFIG_COMPAT |
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long ret; |
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if (is_compat_task()) { |
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ret = compat_arm_syscall(regs, scno); |
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if (ret != -ENOSYS) |
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return ret; |
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} |
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#endif |
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return sys_ni_syscall(); |
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} |
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static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn) |
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{ |
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return syscall_fn(regs); |
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} |
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static void invoke_syscall(struct pt_regs *regs, unsigned int scno, |
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unsigned int sc_nr, |
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const syscall_fn_t syscall_table[]) |
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{ |
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long ret; |
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if (scno < sc_nr) { |
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syscall_fn_t syscall_fn; |
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syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; |
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ret = __invoke_syscall(regs, syscall_fn); |
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} else { |
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ret = do_ni_syscall(regs, scno); |
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} |
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if (is_compat_task()) |
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ret = lower_32_bits(ret); |
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regs->regs[0] = ret; |
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} |
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static inline bool has_syscall_work(unsigned long flags) |
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{ |
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return unlikely(flags & _TIF_SYSCALL_WORK); |
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} |
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int syscall_trace_enter(struct pt_regs *regs); |
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void syscall_trace_exit(struct pt_regs *regs); |
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static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, |
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const syscall_fn_t syscall_table[]) |
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{ |
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unsigned long flags = current_thread_info()->flags; |
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regs->orig_x0 = regs->regs[0]; |
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regs->syscallno = scno; |
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/* |
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* BTI note: |
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* The architecture does not guarantee that SPSR.BTYPE is zero |
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* on taking an SVC, so we could return to userspace with a |
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* non-zero BTYPE after the syscall. |
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* |
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* This shouldn't matter except when userspace is explicitly |
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* doing something stupid, such as setting PROT_BTI on a page |
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* that lacks conforming BTI/PACIxSP instructions, falling |
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* through from one executable page to another with differing |
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* PROT_BTI, or messing with BTYPE via ptrace: in such cases, |
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* userspace should not be surprised if a SIGILL occurs on |
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* syscall return. |
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* |
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* So, don't touch regs->pstate & PSR_BTYPE_MASK here. |
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* (Similarly for HVC and SMC elsewhere.) |
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*/ |
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local_daif_restore(DAIF_PROCCTX); |
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if (flags & _TIF_MTE_ASYNC_FAULT) { |
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/* |
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* Process the asynchronous tag check fault before the actual |
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* syscall. do_notify_resume() will send a signal to userspace |
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* before the syscall is restarted. |
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*/ |
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regs->regs[0] = -ERESTARTNOINTR; |
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return; |
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} |
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if (has_syscall_work(flags)) { |
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/* |
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* The de-facto standard way to skip a system call using ptrace |
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* is to set the system call to -1 (NO_SYSCALL) and set x0 to a |
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* suitable error code for consumption by userspace. However, |
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* this cannot be distinguished from a user-issued syscall(-1) |
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* and so we must set x0 to -ENOSYS here in case the tracer doesn't |
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* issue the skip and we fall into trace_exit with x0 preserved. |
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* |
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* This is slightly odd because it also means that if a tracer |
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* sets the system call number to -1 but does not initialise x0, |
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* then x0 will be preserved for all system calls apart from a |
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* user-issued syscall(-1). However, requesting a skip and not |
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* setting the return value is unlikely to do anything sensible |
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* anyway. |
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*/ |
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if (scno == NO_SYSCALL) |
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regs->regs[0] = -ENOSYS; |
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scno = syscall_trace_enter(regs); |
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if (scno == NO_SYSCALL) |
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goto trace_exit; |
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} |
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invoke_syscall(regs, scno, sc_nr, syscall_table); |
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/* |
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* The tracing status may have changed under our feet, so we have to |
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* check again. However, if we were tracing entry, then we always trace |
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* exit regardless, as the old entry assembly did. |
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*/ |
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if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { |
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local_daif_mask(); |
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flags = current_thread_info()->flags; |
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if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) |
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return; |
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local_daif_restore(DAIF_PROCCTX); |
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} |
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trace_exit: |
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syscall_trace_exit(regs); |
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} |
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static inline void sve_user_discard(void) |
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{ |
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if (!system_supports_sve()) |
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return; |
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clear_thread_flag(TIF_SVE); |
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/* |
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* task_fpsimd_load() won't be called to update CPACR_EL1 in |
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* ret_to_user unless TIF_FOREIGN_FPSTATE is still set, which only |
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* happens if a context switch or kernel_neon_begin() or context |
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* modification (sigreturn, ptrace) intervenes. |
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* So, ensure that CPACR_EL1 is already correct for the fast-path case. |
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*/ |
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sve_user_disable(); |
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} |
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void do_el0_svc(struct pt_regs *regs) |
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{ |
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sve_user_discard(); |
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el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table); |
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} |
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#ifdef CONFIG_COMPAT |
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void do_el0_svc_compat(struct pt_regs *regs) |
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{ |
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el0_svc_common(regs, regs->regs[7], __NR_compat_syscalls, |
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compat_sys_call_table); |
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} |
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#endif
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